Motor control and brake system



May 4, 1943. G. F. PURIFOY MOTOR CONTROL AND BRAVKE SYSTEM Filed March 19, 1942 web Qu Q INVENTOR 6mp/912 @rf/o y.

Patented May 4, 1943 MOTOR CONTROL AND BRAKE SYSTEM George R. Purifoy, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a 'corporation of Pennsylvania.

Application March 19, 1942, Serial No. 435,378

8 Claims.

My invention relates, generally, to motor control systems and, more particularly, to systems for automatically controlling the acceleration and the deceleration of the propelling motors of electric vehicles.

An object of my invention, generally stated, is vto provide an automatic control system for electrically-propelled vehicles which shall be simple and eiicient, in operation and which may be economically manufactured and installed.

A more specific object of my invention is to provide a system suitable for controlling the operation of a single car or two or more cars operating in multiple.

Another object of my invention is to coordinate the electrical-brake and the air-brake systems of an electrically-propelled vehicle.

dynamically braking an electrically-propelled vehicle.

A still further object of my invention is to provide for controlling the dynamic braking rate of a plurality of electrically-propelled cars operating in multiple Without increasing the number of train line wires required.

Still another object of my invention is to provide for changing the dynamic braking rate of vehicles controlled by either unit switch control or multi-notch accelerator control.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of my invention, both the acceleration and the deceleration of electrically-propelled vehicles are automatically controlled by variable rate current limit relays, the setting of which may be adjusted while the vehicles are in operation. The accelerating rate is controlled by means of a master controller and the dynamic braking rate is controlled by means of variable pressure relays `operating from the air-brake system, thereby ksystem embodying my invention, and

Fig. 2 is a chart showing the sequence of operation of a portion of the apparatus 'illustrated Yin Fig. 1.

Referring to the drawing, a pair of electric motors I0 and II may be utilized for propelling a vehicle (not shown). The motor Ill is provided with an armature winding I2 and a series field Winding I3. Likewise, the motor II is provided with an armature winding I4 and a series field winding I5. A line switch IS is provided for connecting the motors III and II to a trolley I6 which engages a power conductor Il that may be energized from any suitable source of power, such as a generating station (not shown).

The motors Ill and II are connected in parallel-circuit relation during acceleration of the vehicle and they may also be connected for dynamic braking with the field winding I5 of motor II connected across the armature I2 of motor I0 and the field winding I3 of motor III connected across the armature I4 of motor I I, thereby permitting the current in the armature wind-'- ings to reverse and cause the motors to act as generators and decelerate the vehicle. A pair of switches BI and B2 is provided for establishing the dynamic braking connections.

Both the acceleration and deceleration of the motors I Il and II are primarily controlled by a motor driven accelerator A which is of the same general type as the one described in Patent No. 1,991,229, issued February 12, 1935, to L. G. Riley, and assigned to the Westinghouse Electric 8: Manufacturing Company. The accelerator A comprises a circular bus I8 inside of which is disposed a plurality of contact fingers 2| to 40, inclusive, which are progressively forced against the bus I8 by a pair of revolving rollers I9 and 20.

The rollers I9 and 20 are driven by a pilot motor PM through shafts 4I and 42 connected by bevelled gears 43. The pilot motor PM is provided with an armature winding 44 and two field windings 45 and 46, one for each direction of rotation of the motor. The energy for operating the pilot motor and the control apparatus may be supplied by a battery or other suitable source of control energy.

A limit relay LR is provided for controlling the operation of the pilot motor PM during both acceleration and deceleration of the vehicle. As shown, the relay LR is provided with several different actuating coils which function to operate the relay during coasting of the vehicle as well as during acceleration and dynamic braking. Thus a coil 41 is connected in the motor circuit during acceleration, and an additional coil 48 is connected in the motor circuit during dynamic braking of the vehicle. A spotting coil 49 is connected across a resistor 5I to be energized in ac- .contact fingers.

ing operations.

of the relay LR, thereby governing the rate of acceleration of the vehicle by varying the speed of the pilot motor PM which,in turn, controls the rate at which resistance is shunted fro-m the motor circuit to vary the motor current, electromechanical means comprising a pair of springs 5t and 55 and a pair of electromagnets 55 and 5'! for tightening the springs 54 and 55, respectively,

is provided. As fully described in Patent No.

2,254,911, issued September 2, 1941 to L. G. Riley, .the energization of the electromagnets 56 and 5l is controlled by a manually opera-ble master controller MC, thereby permitting the operator to vary'the rate of acceleration of the vehicle as desired.

The accelerator A is provided with resistors 53 and 59 for controlling the current in the motors i and i l. The resistor 58 is divided into a number of subdivisions which are connected to the contact ngers 2| to 35, inclusive, and the resistor 59 is divided into subdivisions which are connected to the contact fingers 3l to 0, inclusive. In the present system, the resistors 58 and ,58 are connected in the motor circuit in seriesf circuit relation during both acceleration and dynamic braking, thereby making it unnecessary to change the resistor connections when transferring from motoring to braking operation.

described in the aforesaid Patent No.I

As 2,254,911, the resistor 5I and an additional resistor 6i are connected in the motor circuit in parallel-circuit relation to the resistors 58 and 59 during the motoring operation. Since part of thel motor current is diverted through the resistors 5I and 6|, the heating effect on the accelerator is reduced and also arcing of thecontact iingers onv the accelerator is reduced.

As shown, the accelerator A is provided, with a drum switch 62 having a plurality of contact segments 63Ato 61, inclusive, and cooperating contact fingers which engage the contact segments as'the accelerator is driven by the shaft 52. The reference numerals 2 l to 3D indicate the contact fingers over which the roller I9 travels while the contact segments are engaged by their respective It will be seen that the roller travels over fingers 3l to di) while the roller I9 travels over fingers 2l to 3D. The function of the different segments of the drum switch 62 will be explained more fully hereinafter.

In addition to the accelerator and the control switches previously mentioned, numerous other switches are provided and perform certain switch- These include a switch L for connecting the motors in parallel-circuit relation, a switch MI for connecting the motors to the accelerator during acceleration of the vehicle, a switch G for connecting the accelerator resistors vto ground during acceleration, a switch M2 for connecting the motors directly to ground through the switch G after the accelerator resistors have been shunted from the motor circuit bythe accelerator rollers, and a switch R for connecting the resistors 5l and 6l in thevmotor circuit during acceleration, as previously oescribed.

In order to permit the present system to be utilized on cars which are operated in multipleunit trains and controlled from one control station at the head of the train, a braking relay BR is provided. The relay BR permits dynamic braking to be established simultaneously on all the cars of a train. The energization of the relay BR is controlled by a braking controller BC which may also be utilized to control the airbrake systemV (not shown) Thus when the braking controller at the head of the train is operated, all of there-lays BR throughout the train are energized Vto permit dynamic braking to be established on all the motors in the train. The controllers MC and BC are electrically interlocked to prevent improper operation of the equipment.

As described in the aforesaid Patent No. 2,254,911, a coasting relay CR is utilized to provide smoother operation of multiple-unit trains when power is reapplied tothe motors in the train after a stop has been made by means of dynamic braking. The actuating coil of the relay CR is energized only during spotting or braking of the train and the relay functions to prevent the accelerator from starting to advance while the train is standing still since the coil of the relay CR is responsive to the counter-electromotive force of the motor.

It has been found that in multiple-unit trains the accelerators may start spotting as a result of the operation of the limit relay LR if the operator moves the braking controller to the "o if position while the train is standing still. Thus, when power is reapplied to the motors by operating the master controller, the accelerators may not all be in the correct position for the reaplplication of power, thereby resulting in rough or uneven operation of the train. Since the relay CR is responsive to the motor speed, its contact members are so connected in the motor circuit that the advancement of the accelerator is preventedwhile the train is standing still.

In order to coordinate the operation of the airbrake system and the dynamic braking of thevehicles, an air-operated relay C is provided on each vehicle of a train. As indicated in the drawing, the relays C are connected to the air line of the air-brake system and each relay is, therefore, responsive to the airbrake pressure which is controlled by the braking controller BC. The relay C is provided with contact members which successively shunt portions of a resistor 68 from the circuit for the rate coil 52 on the limit relay Vtem is obtained by supplying maximum air pressure to the braking system, it will be seen that .the maximum eiect of the electrical or dynamic braking system is likewise obtained as a result of the application of maximum air pressure to the braking system.v rThe relay C is so con- .structed that more of the resistor 68 is shunted from the circuit for the rate coil 52 as the air pressure increases, thereby changing the setting of the relay LR -to permit an increase in the braking current andV the braking effect of the motors. In thisY manner, the electrical or dy,- namic braking system is coordinated with the air-brake system and both systems are under the control of the operator atV all times.

In order that the functioning of the foregoing apparatus may be more clearly understood the operation of the system will now be described in more detail. Assuming that it is desired to accelerate the vehicle at the maximum rate, the master controller MC is actuated to position 4, thereby applying power to the motors and |I.

When the controller MC is actuated to position I, the switches LS, L, MI, R and G are closed to connect the motors |0 and II to the power source in series-circuit relation with the resistors 58 and 59 of the accelerator A. The energizing circuit for the actuating coil of the switch LS may be traced from positive through a contact segment 1| of the controller MC, conductor 12, an interlock 13 on the switch BI, conductor 14, the actuating coil of the switch LS, conductor 15 and the contact segment 66 of the drum switch 62 on the accelerator A to negative. Following the closing of the switch LS, a holding circuit for the actuating coil is established through an interlock 16 to negative.

The energizing circuit for the switch L is also established by the closing of the switch LS. This circuit extends from the conductor 14 through an interlock 11 on the switch LS, conductor 18 and the actuating coil of the switch L to negative. The energizing circuit for the switch Ml extends from the conductor 14, through the actuating coil of the switch MI to negative. Likewise, the energizing circuit for the switch R extends from the conductor 14, through the actuating coil of the switch R to negative. The energizing circuit for the switch G also extends from the conductor 14, through the actuating coil of the switch to negative.

As explained hereinbefore, the resistors 5I and 6| are connected in the motor circuit in parallelcircuit relation to the resistors of the accelerator A during the motoring operation, thereby reducing the duty imposed upon the accelerator and also making it possible to connect the resistors 58 and 59 of the accelerator in series-circuit relation during motoring as well as during dynamic braking which simplifies the switching operations necessary to establish dynamic braking of the motors. The resistors 5| and 6I are connected in the motor circuit by the closing of the switch R.

Further acceleration of the motors I 0 and I I is controlled by the accelerato-r A which is driven by the pilot motor PM under the control of the limit relay LR. The pilot motor is energized at this time through a circuit which may be traced from positive, through a resistor 19, conductor 8|, the tickler coil 53 of the relay LR, contact members 82 and B3 of the relay LR, conductor 84, an interlock 85 on the switch G, conductor 86, an interlock 81 on the switch M2, conductor 88, the segment 64 of the drum switch 62 on the accelerator A, conductor 89, the eld winding 45 of the pilot motor PM and the armature winding 44 to ground.

As explained hereinbefore, the pilot motor PM advances the accelerator A under the control of the limit relay LR, the operation of which is governed by the motor current. The coil 41 of the relay LR is connected in the circuit for the motor |I during acceleration and is, therefore, responsive to the motor current.

Since it has been assumed that the master controller MC is actuated to position 4, both of the electromagnets 56 and 51 are energized to apply Vtension to the springs 54 and 55, respectively, 'thereby increasing the current required to operate the relay LR which, in turn, increases the current supplied to the motors l0 and I| to increase the rate of acceleration. The energizing circuit for the electromagnet 56 may be traced from the controller MC, through conductor 9| and the coil of the electromagnet 56 to negative. The energizing circuit for the electromagnet 51 extends from the controller MC, through conductor 92 and the coil of the magnet 51 to negative.

When the accelerator A nears the end of its travel in the forward direction, the switch M2 is closed to connect the motors |0 and I I directly to ground. The energizing circuit for the actuating coil of the switch M2 may be traced from the controller MC, through conductor 93, an interlock 94 on the switch LS, conductor 95, an interlock 96 0n the switch B2, conductor 91, the actuating coil of the switch M2, conductor 98 and the contact segment 61 of the drum switch 62 to negative. A holding circuit for the coil of the switch M2 is established through an interlock 99 carried by the switch M2.

The closing of the switch M2 connects the motors |0 and directly to ground through the switch G, thereby permitting the accelerator A to be returned to its initial position in preparation for the establishment of the dynamic braking circuit for the motors. The closing of the switch M2 opens its interlock 81, thereby interrupting the energizing circuit for the pilot motor which operated the motor in the forward direction. Furthermore, the closing of the switch M2 energizes the off field winding 46 of the pilot motor, thereby causing it to operate in the reverse direction to return the accelerator A to its initial position. At this time, the energizing circuit for the pilot motor may be traced from positive, through the resistor 19, conductor BI, an interlock IIll on the switch M2, conductor |02, the contact segment of the drum switch 62, conductor |03, the field winding 46 of the pilot motor PM and the armature winding 44 to ground.

AS the pilot motor approaches its initial position, the motor is deenergized by the interruption of the circuit through the segment 65 of the drum switch 62. Furthermore, an electrical braking circuit is established for the motor to bring it to a quick stop at the end of its travel. The braking circuit may be traced from one terminal of the armature 44, through the iield winding 45, conductor 89, the contact segment 64 of the drum switch 62, conductor 88, an interlock |04 on the switch M2, conductor |05, the segment 63 of the drum switch 62, conductor |06, a portion of a resistor |01 and thence to the -other terminal of the armature winding 44, through the ground connection.

A similar braking circuit for the motor PM was established upon the interruption of power to the motor by the opening of the contact members of the limit relay during the operation of the accelerator in the forward direction. This braking circuit may be traced from the one terminal of the armature winding 44, through the iield winding 46 of the motor, conductor |63, an interlock |08 on the switch M2, conductor |09, the resistor I 01 and thence to the other terminal of the armature winding 44, through the ground connection.

If it is desired to permit the vehicle to coast the motors I0 and may be disconnected from the power source by actuating the controller MC to the off position, thereby deenergizing the actuating coils for the switches LS, L, MI, R, G and M2. When the controller MC is returned to the o position, the switches BI, B2 and L are closed Ito.,estalolish, a dynamic'brakingcircuit for the motorsprovided the accelerator A khas, re-

turned to .its initial position tov insert the full amount of Yits;resistance in the motor circuit. In this manner, v`a snj1al 1amount of current iS, permitted to circulate through the motors during coasting of the vehicle as described in Patent No. 2,078,684, issuedApril 27, l 937, to L. G. Riley. However, the circulating current isof such a low value that it does not materially affect the coasting characteristics of the Vehicle. vThe energizing circuit for the actuating coil of the switch BI may be traced from positive, through a contact segment I I I on the controller BC which is in the release position, conductor H2, a segment I'I3 on the controller MC, conductor I I4, anl interlock I i 4on the switch LS, conductor I It, the actuating coil of the switch Bi conductor 'I5 and the segment G5 von the drum switch S2 to negative. The energizing circuit for the actuating coil of the switch B2 kextends from the conductor I Ii,V through the coil of the switch B2 and thence to negative through ,conductor l5 and the segment 66, as previously ldescribed. A holding circuit for the switches BI and B2 is established through an interlock Ii :carried by the switch Bl. The energizing circuit .for the switch L extends from the conductor l Iii, through an interlock I2l on the switch Bl, con- ;ductor I8 and the actuating coil of the switch L itc negative.

During coasting the generated current is main- :tained at a relatively low value by the action of the accelerator A which is under the control of ,the limit relay LR during coasting, the relay LR.

being operated by the spotting coil 59 which is g connected across the resistor 5I which isin the motor circuit at this time. The spotting coil 49 is designed to operate the relay at` a relatively low value of current and theelectromagnets 56 and 5l are deenergized atthis time to remove the tension from the springs 54 and 55. The energizing circuit for the spotting coil49 may be raced from one terminalof the resistor 5l, through conductor Il, an interlock IIS on the switch G, conductor I2i, the spottingA coil dll, conductor |22, Contact members E23 ofthe relay BR, conductor I24 to the other terminal'of the resistor 5I.

Since the current generated by the machines I0 and II during coasting i's proportional to the a2 teenage' a celiaci menta "las tf the` "relay itsinitial position, thereby increasing the 're- Y sistance-in the motor circuit and matchingithe position 'ofthe accelerator withthe speed of the speed of the vehicle, this current may beutilized for spotting the accelerator A, that is matching the position of the accelerator with the speed of the vehicle, thereby insuring that the accelerator will be in the proper position for the utilization of dynamic braking to decelerate the car. As previously explained, the'accelerator is under the control relay of the limit relay LR during coasting. The Contact members of thelimit relay are so connected in the circuit for the pilot motor that the motor may be operated in either direc tion depending upon the speed of the car. Thus, with the contact members 82' and 83 closed, the pilot motor advances the accelerator Ito decrease the resistance vin the motor circuit until the point is reached at which the motor lcurrent is suii- .cient to operate the relay LR to open the contacts 82 and 83. Should the car decrease in speed, which would result in lower motor current, the contact members 82 and 83 are closed to further advance the accelerator. Y

However, should the car increase in speed iduring coasting, resulting in a suflicient increase in v'the motor current to cause the contactmember `car. ,The circuit for vforward operation of the pilotmotorrmay vbe traced from positive, thlQllgh the resistor T9, conductor BI, tickler coil 5 3, contact members 82 and 83, conductor 84, contact members [25 0f the relay CR, conductor 86, interlock Sl on the switch M2, conductor V83, the segment B on the drumswitch 62, conductor 8S, the fon iield winding `450i the pilot motor andthe armature winding ll to ground. The Acircuitfor reverse operation extends from thecontact member |25 through conductor |92 to the drum switch S2 and thence to the pilot motor, as previously traced. Y

, As explained hereinbefore, the relay CR is utilized to permit operation oi theaccelerator during coasting and braking but'to prevent its advancement while the vehicle is standing still. The operating coil for the relay CR is connected across one motor to ground, thereby being'enervgized by the counter-electromotive force of the motor which is dependent upon the speed of rotation of the motor. The energizing circuit for the coil of the relay CR may. be traced from one terminal of the armature i4 of the motor II through the coils l' and l of the relay LR, conductor $27, the switch BI, conductor |25, the resistor 5l, conductor I I8, interlock Iig on the switch conductor l2 I, the coil of the relay CR, conduct-o1l 23, contact members of the relay BR, conductor ISI and an interlock |32 on the switch G to ground.

Thus, it will be seen that while the vehicle is Vmoving the relay CR is energized to close its'contact members IZB, thereby permitting the limit relay LR to spot the accelerator in the manner hereindescribed. However, when the vehicle is standing, the relay CR is deenergized and the circuit for the forward operation of the lmotor PM is interrupted by the opening of the contact members 426 which prevents the accelerator from being advanced as a result oan operation ci the Y relay LR which, of course, would normally operateV tol advance the accelerator since the motor current is below the setting of the spotting coil i9 of the relay.

Furthermorawhen the relay CR is deenergized,

' a circuit is established to operate the accelerator in the reverse direction to 'return it to its initial position. This circuit may be traced from the conductor 8l, through an interlock |33 on the switch LS, conductor 53?, contact members I35 i operation during dynamic'braking, since the rate coil 522 opposes the action of the coils 41 and 48 on the relay. The relay CR is also recalibrated by the opening of the contact members |29 on the relay BR to insert a resistor |37 in the circuit ,for the 'coil 'of theY relay CR. Th energizing circuit for the actuating coil of the relay BR may be traced from the previously energized conductor I I4, through a segment |38 on the controller BC, conductor |39, an interlock |4| on the switch Bl conductor |42, and the actuating coil of the relay BR. to negative.

During braking, the calibration of the relay LR is governed by the energization of the rate coil 52 which is connected across the resistor 5|, through a circuit which may be traced from one terminal of the resistor 5|, through conductor I I8, the interlock I9 on the switch G, conductor |2I, contact members |44 on the relay BR', conductor |45, the resistor 68, conductor |46, the rate coil 52 and conductor |24 to the other' terminal of the resistor 5|.

As explained hereinbefore, the operation of the braking controller BC to one of the braking positions admits air pressure to the braking system and to the relay C, the pressure depending upon the position to which the controller is actuated.

When air pressure is applied to the relay C its contact members are closed to shunt portions of the resistor 68 from the circuit for the rate coil 52, the amount of resistance being shunted depending upon the pressure applied to the relay C. The shunting of the resistor 68 changes the calibration of the relay LR, thereby controlling the dynamic braking rate. Thus, if maximum braking effect is desired by the operator, in which event he will operate the brake controller to provide maximum air pressure, the relay LR is automatically calibrated to provide maximum dynamic braking eiect on the vehicle, thereby securing the maximum total braking effect possible. In this manner the air-brake system and the electrical or dynamic braking system are coordinated at all times and the total braking effect on the vehicle is under the control of the operator,

It will be noted that the switch M2 is closed in the event that the accelerator is fully advanced to shunt the resistors 58 and 59 from the motor circuit during dynamic braking in a manner similar to that during acceleration of the vehicle. The energizing circuit for the actuating coil of the switch M2 extends from the previously energized conductor |42, through an interlock |41 on the switch B2, conductor 9T, the actuating coil of the switch M2, conductor 98, and thence to negative at the drum switch 62 as previously traced.

While I have illustrated and described my control system as being applied to a vehicle controlled by a motor driven accelerator, it will be i understood that the present system is clearly applicable to a system in which the acceleration and dynamic braking of the vehicle are controlled by unit switches, the operation of which is controlled by a current limit relay in a manner well known in the art.

Furthermore, it is to be understood that the present system may be readily applied to the control of a plurality of vehicles operating in trains, the equipment on each vehicle being a duplicate of that illustrated and described. The vehicles are electricaliy connected by a group of train line wires, as indicated in the present drawing. The air-brake system is connected between vehicles in the usual manner.

From the foregoing description, it is apparent that I have provided for the coordination of the air and the electrical braking systems in a simple and effective manner which does not increase the number oi train line wires required for controlling a plurality of vehicles and which does not materially increase the equipment required for controlling the operation of the vehicles.

Since many modications may be made in the apparatus and arrangement of parts without departing from the spirit of my invention, I do not wish to be limited other than by the scope of the appended claims.

I claim as my invention:

1. In a motor control system, in combination, a motor for propelling a vehicle having an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, relay means responsive tothe motor current for controlling the rates of acceleration and deceleration of the vehicle, and means responsive tothe pressure in the air-brake system for controlling the operation of said relay means.v

2. In a motor control system, in combination, a motor for propelling a vehicle having an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, relay means responsive to the motor current for controlling the rates of acceleration and deceleration of the vehicle, and a relay responsive to variations in the pressure inthe air-brake system for controlling the operation of said relay means.

3. In a motor control system in combination, a motor for propelling a vehicle having an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, control means for controlling the motor current during acceleration and deceleration of the vehicle, relay means responsive to the motor ,current for controlling the operation of said control means, and an air pressure relay responsive to the pressure in the air-brake system for controlling the operation of said relay means.

4 In a motor control system, in combination, a motor for propelling a vehicle having an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, control means for controlling the motor current during acceleration and deceleration of the vehicle, relay means responsive to the motor current for controlling the operation of said control means, and an air pressure relay having contact members actuated in sequential relation by the pressure in the air-brake system for controlling the operation of said relay means.

5. In a motor control system, in combination, a motor for propelling a vehicle having an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, control means for controlling the motor current during acceleration and deceleration of the vehicle, relay means responsive to the motor current for controlling the operation of said control means, a controller for varying the pressure inthe air-brake system'of the vehicle, and means ,responsive to the ,pressure in Ythe air-brake system for controlling the operation vof vsaid relay means.

-6. Ina motor Vcontrol system, in combination, a motor for propelling a vehicle Ahaving an airbrake system, a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, additional switching means for establishing dynamic A,braking Connections for the motor to decelerate the vehicle, Acontrol means for controlling the motor current during racceleration and deceleration of the vehicle, relay vmeans responsive to the motor current for `controllingthe operation of said control means, a controller for varying .the pressure in the air-'brakesystem of the vehicle, .and means .responsive to the ,pressure in the air-brake system Vfor controlling the operation of said relay means, said controller also controlling the operation of the vswitching means for establishing dynamic braking connections for the motor.

7. In a motor control system, in combination, a motor for propelling a vehicle having an airbrake system, aI power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, a master controller for controlling `the operation of said switching means, additional switching means for establishing dynamic connections for the motor to deceleratethe vehicle, control' means for controlling the motor current during acceleration and deceleration of the vehicle, relay vmeans re- -sponsive to the motor current for controlling the operation of said control means, said master controller also controlling the operation of said relay means during acceleration of the vehicle,

.a braking controller for varying the pressure in the air-brake system, and means responsive to the pressure in the air-brake system for controlling the operation of said relay means during deceleration of the vehicle.

8. In a motor control system, in combination, a `motor for propelling a vehicle having an airbrake system, ,a power conductor, switching means for connecting the motor to the power conductor to accelerate the vehicle, a master 4controller for controlling the operation of said vswitching means, additional switching means for establishing dynamic connections for the motor to decelerate the vehicle, control means for controlling t'ne motor current during acceleration and deceleration of the vehicle, relay means re- `'sponsive to the motor current for controllingthe operation of said control means, said master controller also controlling the operation of said relay vmeans during acceleration of the vehicle, a braking controller for varying the pressure in the air-brake system, and means responsive to the pressure in the air-brake system for controlling the operation of said relay means during Adeceleration of the vehicle, said braking controller also controlling the operation of the switching means for establishing dynamic braking connections for the motor.

GEORGE R. PURIFOY. 

